Consider the accuracy of temperature measurement over the last hundred years.
The very idea of an absolute zero wasn't even seriously discussed until the second half of the ninteenth century. Actually approaching it has been a matter not accomplished until the 1970's : http://home.comcast.net/~igpl/Temperature.html
Most of the readings were taken by humans reading thermometers and writing down the results. Can you say "human error"?
Couple that with the instrumentation changes made over the last century, like the addition of back mirrors to eliminate paralax error, and you begin to understand that any consideration of humans being capable of DETECTING a global temperature rise, much less actually having an effect on it, is quite preposterous.
Thermal readings are being taken from places like airport runways near jetwash areas and next to heat pump installations. NASA has been caught with it's pants down over a Y2K glitch in a program reporting sattelite temperature readings which falsely made the 1990's the hottest on record.( It was actually the 1930's once corrected.)
Reference makers can't even agree on what the standard should be for room temperature.(68 or 72 degrees?) There are competing scales of measurement that must be converted from nation to nation. Inaccuracies abound.
The fact that there have been "little ice ages" and "little warm periods" in the Holocene era, before mankind had the current level of carbon generating capacity, makes the idea of manmade global warming silly and arrogant. :http://www.ucmp.berkeley.edu/quaternary/hol.html
Now think about the fact that Mount Saint Helens spewed more "greenhouse" gasses into the atmosphere in one day than humanity has in our entire recorded history. Did we die of a heat death then? One volcanic eruption, one day, more than all we've ever done.......
When you add to these things the additional factors of orbital changes and cosmic dust clouds impacting solar content absorption, and the solar flare activity during solar maximum and maunder minimums, it becomes clear that human impact on climate is irrelevant.
The cosmos dishes out what it dishes out. We must learn to adapt or perish.